The present invention relates to load carrying means for cable elevators with integrated load measuring equipment, in which the weight of the load carrying means and the useful load being carried causes a load-proportional deformation of at least one resilient element, wherein at least one sensor detects this deformation and generates, at an elevator control, a signal representing the amount of the deformation and thus the load.
Load measuring equipment for load carrying means of elevators has the task of preventing elevator travel with an impermissibly high load and of delivering, to the elevator control, data which enables the control to react, independently of the instantaneous load state of the load carrying means, in suitable manner to call commands by elevator users.
The European patent document EP 0 151 949 shows load measuring equipment for an elevator which is based on the principle that the entire elevator car is supported on at least four bending girders projecting from an elevator car base frame in such a manner that these bending girders experience a load-proportional bending deflection. The bending deflection of each individual bending girder is detected by means of strain gauges. All strain gauges form in common a measurement bridge that delivers a load-proportional analog signal to the elevator control.
The above-described prior art load measuring equipment has some disadvantages. The measuring principle requires four bending girders each equipped with a respective strain gauge or two respective strain gauges, wherein the mechanical tolerances of the bending girders as well as the resistance tolerances and mounting tolerances of the strain gauges have to be closely limited in such a manner that all four bending sensors have the same resistance values for the same loads. All four or eight strain gauges have to be individually connected with a central evaluating circuit, which occasions substantial cost. Moreover, the four force introduction points between the base of the elevator car and the bending girders have to be adjusted in vertical direction when being mounted so that an acceptable force distribution is ensured.
The present invention concerns a load carrying means for cable elevators including: a support construction adapted to be attached to an underside of a base frame or a carrier frame for an elevator car; a pair of cable rollers positioned below the support construction; a resilient element attaching at least one of the cable rollers to the support construction whereby when the support construction is attached to the underside of the elevator car and the cable rollers are engaged by a support cable supporting the elevator car, the resilient element is deformed by load-dependent cable forces acting on the resilient element through the at least one cable roller; and a sensor means for detecting the deformation of the resilient element. The load carrying means also can include a resilient isolating means attached to the support construction and adapted to be attached to the base frame or the carrier frame.
The present invention is based on the object of creating simple and economic load measuring equipment for loading carrying means of elevators with underslung cable drive, which does not have the above-mentioned disadvantages.
The load carrying means according to the present invention for cable elevators with integrated load measuring equipment has significant advantages. The detection of the total weight of the load carrying means and thus also the useful load is carried out by means of a single sensor, wherein even eccentrically disposed useful loads are correctly detected by this. Thus, costs for further sensors, for the wiring thereof and for the complicated signal evaluation thereof are saved. The resilient element, the deformation of whichxe2x80x94caused by the weight of the load carrying meansxe2x80x94is detected by the sensor, is part of the support construction by which the cable rollers are fastened to the load carrying means. Consequently, substantially no additional mechanical constructional elements and no additional insulation space are needed for the load measuring equipment.
The resilient element, the load-dependent deformation of which is detected by a sensor, can be conceived for different forms of loading, i.e. it can be designed as, for example, a bending girder, a tension/compression rod, a torsion rod or, for attainment of greater deformation travels, a compression, tension or torsion spring. Thus, load measuring equipment optimally adapted to different forms of load carrying means can be constructed.
Advantageous and economic embodiments of the load carrying means according to the present invention with integrated loading measuring equipment can be achieved through use of sensor principles adapted to geometric relationships, environmental influences and, in particular, demands on accuracy. The invention permits use of the most diverse sensors for deformation detection, such as, for example, strain gauges, vibrating string sensors, opto-electrical distance or angle sensors and inductively or capacitively functioning distance sensors.
Depending upon the form of the load carrying means it can be advantageous to allow the two cable rollers mounted below the load carrying means to act directly on a common resilient element. The advantages can be a symmetrical, simple execution of the support construction between the cable rollers and the load carrying means for improved deformation measurement possibilities.
In the case of restrictive geometric relationships in the vicinity of the underlying cable rollers, or in the case of selection of specific forms of sensor, it can be advantageous to allow only one of the two cable rollers to act on a resilient element. The support constructions for the two cable rollers can in that case be executed as separate and differently formed units and no mechanical connections between these units are required. Such embodiments are made possible by the fact that in the case of the underslung arrangement, in accordance with the present invention, of the support cables both cable rollers always experience the same loading.
Load carrying means for greater loads are usually equipped with a carrier frame. In the case of such embodiments it is generally of advantage to fasten the support construction or constructions, which contains or contain the resilient element and which supports or support the cable rollers, to this carrier frame.
In the case of load carrier means for smaller useful loads, these can be executed as a self-supporting unit. The support construction or constructions carrying the cable rollers and containing the resilient element is or are in that case in an advantageous manner fastened directly to the base construction of the load carrying means.
In order to reduce the transmission of vibrations and sound waves from the support cables to the load carrying means it is advantageous to arrange isolating elements between the load carrying means and the support construction or constructions for the cable rollers.